1. Field of the Invention
The present invention relates to a voltage smoothing circuit, a method for controlling a voltage to be applied to a multilayer capacitor that is included in the voltage smoothing circuit, and a voltage conversion circuit.
2. Description of the Related Art
Increase in capacitance of a multilayer ceramic capacitor has been advanced to thus enable a power supply voltage of an electronic apparatus to be used as a smoothing capacitor. Further, with recent advancement in size reduction of the electronic apparatus, usage of the multilayer ceramic capacitor having large capacitance and reduced in size has further increased. Ceramic materials used in the multilayer ceramic capacitor have piezoelectricity and an electrostrictive property. Accordingly, distortion is generated thereon when a voltage is applied. In particular, when an alternating current (AC) voltage or a direct-current (DC) voltage on which an AC component is superimposed is applied to the multilayer ceramic capacitor having large capacitance, vibration is generated due to the above-mentioned distortion in some cases. This results in vibration of a circuit board on which the multilayer ceramic capacitor is mounted and acoustic noise is generated in some cases.
Japanese Unexamined Patent Application Publication No. 2013-258278 discloses a method for driving a multilayer ceramic capacitor in which a first multilayer capacitor and a second multilayer capacitor are stacked. Japanese Unexamined Patent Application Publication No. 2013-258278 indicates that the above-mentioned acoustic noise is suppressed by driving the first multilayer capacitor and the second multilayer capacitor in opposite phases.
However, distortion on the first multilayer capacitor and distortion on the second multilayer capacitor cannot be completely cancelled by each other even by using the driving method as described in Japanese Unexamined Patent Application Publication No. 2013-258278. Accordingly, when a circuit is formed using the above-mentioned multilayer capacitor, distortion tends to be generated on an output voltage.